DWORD
0—Turns off Vault Cache for this user. No new Vault Cache is created.
The user has access to an existing Vault Cache, but no new items are
added to an existing Vault Cache.
1 — (Default) The user can enable Vault Cache.

Controls whether the user can enable Vault Cache.

Note: This registry value performs the same function as the Exchange
desktop policy setting “Make Vault Cache available for users”, which
you can set through the Administration Console. For more information
on the policy setting, see Setting up Exchange Server archiving.

Well the VaultCacheStoreID is a hexadecimal value based on the current Outlook profile. Essentially it facilitates having multiple Vault Cache configurations across multiple Outlook profiles in a single Windows profile.